The present invention generally relates to a program-controlled shutter and more particularly to a program-controlled shutter of the type in which a plurality of shutter blades which also function as the aperture control blades, are opened to define a desired aperture or f-number, for a desired time, depending upon the brightness of a subject.
In the typical conventional program-controlled shutter, in response to the brightness of a subject, the aperture blades which are located before or after the shutter blades are opened or closed by suitable driving means, and thereafter, the exposure time is determined as a function of the apertures set. The automatic aperture blade control means in general consists of a moving coil, and in order to permit the automatic aperture control means to follow the relative fast change in brightness of the subject, it is so designed that its mechanical friction may be minimized. As a result, the automatic aperture control means is easily susceptible to damages due to mechanical shocks or impacts. The conventional program-controlled shutters have another common undesirable feature that is their construction is very complex because both complex aperture control and shutter control mechanisms must be mechanically incorporated.
In the conventional program-controlled shutters, the mechanical energy which is stored when the film is advanced is released to actuate the shutter blades, and a relatively greater force is required to liberate this energy, so that the shutter button depression often results in shaking of the camera.
In order to remotely control the shutter operation, in the conventional shutters by an electrical signal, the shutter release button must be operatively coupled to a suitable solenoid, so that the latter may be energized in response to the remote control signal to depress the shutter release button. However, such an arrangement makes it difficult to attain the desired synchronization between the application or transmission of the control signal and the resulting shutter operation because of the unavoidable time lag between the time when the current starts to flow through the solenoid coil and the time when the solenoid produces the sufficient driving force for depressing the shutter button, and because of the delay in transmission of the driving force to the shutter release button due to the mechanical driving force transmitting mechanism. Furthermore, such a remote control system is very complex, large in size and heavy in weight because of the provision of the solenoid and the mechanical system for coupling the solenoid to the shutter release button.